Add cooked rigatoni in pan (if you do not have room in the pan, pour mixture over bowl of cooked rigatoni and mix well.

Sprinkle with shredded Parmesan cheese

Gail's Comments: My daughter made this without the mushrooms and it was just incredible! I forgot where she found the recipe online.

I made it later on with mushrooms and it was absolutely splendid! However, whatever you do, do not prepare the sauce until you have everything ready (noodles cooked, chicken, caramelized onions, sauteed mushrooms, etc.).